Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 152

not been able to determine clear changes in the intensity and
frequency of storms in the middle latitude regions [IPC 13].
4.3.4.2. Winds, wave climate and sea currents
Wave formation results from the action of winds on the ocean's
surface. When the wind waves propagate over large distances, they
form the swell. The dissipation of energy when the waves break on the
seashore defines the coastline by transporting unconsolidated
sediments and controls the phenomena of erosion, floods and
submersions. Climate change, by modifying the wind regimes and the
trajectories, intensity and frequency of storms, changes the wind wave
climate and the swell, with very significant effects on the coastal
zones. For example, a rotation of the mean direction of the waves can
modify considerably the transport of sediments along the coast and
aggravate the erosion [SAN 02]. A change in the wind regime on the
coast can also change the intensity of upwelling, with significant
effects on biological production and fishing stocks.
Considerable uncertainties remain regarding future projections for
the mean and extremes of winds, waves and swell on the coast,
especially at a regional and local level, obtained from climate models
[IPC 13].
The changes in the general circulation of the atmosphere resulting
from global warming can also change the intensity and direction of
marine currents. For example, the thermohaline circulation in the
North Atlantic that transports heat northward and contributes to
maintain relatively mild temperatures in North-West Europe will very
probably slow in the course of the 21st Century. There too,
uncertainty remains over the evolution of this phenomenon and more
generally over the impacts of climate change on global and regional
oceanic circulation.
4.3.4.3. Sea surface temperature
It has already been underlined that currently the ocean absorbs
more than 90% of the excess thermal energy resulting from the
intensification of the greenhouse effect. This absorption leads to a
warming of the ocean, especially of its upper layers above 700 m in